GitHub Enterprise Server up to 3.22.0 Markdown Rendering cross site scripting

Summaryinfo

A vulnerability labeled as problematic has been found in GitHub Enterprise Server up to 3.22.0. This affects an unknown part of the component Markdown Rendering. Such manipulation leads to cross site scripting. This vulnerability is referenced as CVE-2026-77912. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in GitHub Enterprise Server up to 3.22.0 and classified as problematic. Affected by this issue is an unknown part of the component Markdown Rendering. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. CVE summarizes:

A stored cross-site scripting (XSS) vulnerability was identified in GitHub Enterprise Server that allowed an authenticated attacker to inject arbitrary HTML attributes into rendered Markdown because the Markdown rendering pipeline rewrote quote characters in already-sanitized HTML without re-sanitizing the result. Crafted Markdown could abuse same-origin JavaScript gadgets to bypass Content Security Policy and gain control of the page DOM when viewed by another user. Successful exploitation could allow an attacker to read content visible to the victim, extract embedded CSRF tokens, perform state-changing actions as the victim, and exfiltrate data through same-origin writes. The payload could also propagate to repositories and organizations where the victim had write access. This vulnerability affected supported GitHub Enterprise Server releases in the 3.17, 3.18, 3.19, 3.20, 3.21, and 3.22 series and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported via the GitHub Bug Bounty program.

The advisory is shared for download at docs.github.com. This vulnerability is handled as CVE-2026-77912 since 08/21/2026. The exploitation is known to be easy. The attack may be launched remotely. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 3.17.21, 3.18.15, 3.19.12, 3.20.8, 3.21.6 or 3.22.1 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Bug Tracking Software

Vendor

• GitHub

Name

• Enterprise Server

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4
• 3.5
• 3.6
• 3.7
• 3.8
• 3.9
• 3.10
• 3.11
• 3.12
• 3.13
• 3.14
• 3.15
• 3.16
• 3.17
• 3.17.0
• 3.17.1
• 3.17.2
• 3.17.3
• 3.17.4
• 3.17.5
• 3.17.6
• 3.17.7
• 3.17.8
• 3.17.9
• 3.17.10
• 3.17.11
• 3.17.12
• 3.17.13
• 3.17.14
• 3.17.15
• 3.17.16
• 3.17.17
• 3.17.18
• 3.17.19
• 3.17.20
• 3.18
• 3.18.0
• 3.18.1
• 3.18.2
• 3.18.3
• 3.18.4
• 3.18.5
• 3.18.6
• 3.18.7
• 3.18.8
• 3.18.9
• 3.18.10
• 3.18.11
• 3.18.12
• 3.18.13
• 3.18.14
• 3.19
• 3.19.0
• 3.19.1
• 3.19.2
• 3.19.3
• 3.19.4
• 3.19.5
• 3.19.6
• 3.19.7
• 3.19.8
• 3.19.9
• 3.19.10
• 3.19.11
• 3.20
• 3.20.0
• 3.20.1
• 3.20.2
• 3.20.3
• 3.20.4
• 3.20.5
• 3.20.6
• 3.20.7
• 3.21
• 3.21.0
• 3.21.1
• 3.21.2
• 3.21.3
• 3.21.4
• 3.21.5
• 3.22.0

License

• open-source

CPE 2.3info

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CPE 2.2info

• 🔒
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